text/v2: bug fix: the given slice to MultiFace should be copied

Updates #2845

text/v2/multi.go

@@ -32,9 +32,10 @@ type MultiFace struct {
 
 // NewMultiFace creates a new MultiFace from the given faces.
 func NewMultiFace(faces ...Face) *MultiFace {
-	return &MultiFace{
+	m := &MultiFace{}
-		faces: faces,
+	m.faces = make([]Face, len(faces))
-	}
+	copy(m.faces, faces)
+	return m
 }
 
 // Metrics implements Face.

text/v2/text_test.go

@@ -240,3 +240,14 @@ func TestUnhashableFace(t *testing.T) {
 		}
 	}
 }
+
+func TestMultiFace(t *testing.T) {
+	faces := []text.Face{text.NewStdFace(bitmapfont.Face)}
+	f := text.NewMultiFace(faces...)
+	img := ebiten.NewImage(30, 30)
+	text.Draw(img, "Hello", f, nil)
+
+	// Confirm that the given slice doesn't cause crash.
+	faces[0] = nil
+	text.Draw(img, "World", f, nil)
+}